Device for automatic chemical analysis

ABSTRACT

This invention provides an automated chemical analyzer capable of automatically analyzing a plurality of samples for at least two different analytes. The analyzer includes a plurality of assay resource stations and an analyzer control means. Each assay resource station includes an assay resource capable of performing a predetermined operation upon a sample-containing reaction vessel within a fixed indexing time. The analyzer control means includes scheduling means for allocating assay resources to one of the reaction vessels as a function of that time cycle and a transfer control means for controlling transfer of reaction vessels directly from one assay resource station to another according to a chronology selected from a plurality of different predetermined chronologies.

This application is a continuation of Ser. No. 07/878,956 filed Jun. 5,1992 now U.S. Pat. No. 5,380,487.

FIELD OF THE INVENTION

The present invention relates to automated chemical analysis methods andapparatuses, such as are used in the field of diagnostics. Inparticular, the present invention provides an apparatus and method forefficiently scheduling and performing analytical tests on samples.

BACKGROUND OF THE INVENTION

Automated chemical analyzers have proved to be useful tools in clinicallaboratory settings. Quantitative chemical analysis requires precisecontrol of such factors as time of reaction, temperature and reagentconcentration. Tests manually conducted typically lack precise controlof these parameters resulting in inaccurate or irreproducible results.Additionally, manual testing limits the speed of processing, makes thehandling of large numbers of samples difficult and introduces thepossibility of human error, such as misidentification of samples.

Fully automated chemical analyzers automatically obtain a volume of apatient sample suspected of containing a particular analyte, addreagents to the sample and control reaction parameters such as time andtemperature. Such analyzers usually include a transport or conveyorsystem designed to transport containers of reaction mixtures of sampleand reagents to various operating stations. Reactions between analyte inthe sample and reagents result in a detectable signal automaticallymeasurable by the instrument. The measured value is then compared to acalibration curve that is generally stored in the instrument, todetermine the final test result: the concentration of the analyte in thepatient sample.

A number of automated chemical analyzers are currently available on themarket. These analyzers differ somewhat in the methods by which thesamples and reaction mixtures are processed once they are introduced tothe analyzer by the operator. Volume 14 of the Journal of ClinicalImmunoassay, Summer 1991, ("J. Clin. Immun."), the teachings of whichare incorporated herein by reference, provides a description of severalof such automated analyzers.

Known analyzers differ in the frequency at which new samples or testscan be introduced to the analyzer for analysis. In an instrument with"batch access", a plurality of samples is introduced to the analyzer ina set and a new set of samples can be introduced to the analyzer onlywhen analysis of all the samples in a prior set of samples is completed.In an instrument that has "continuous access," new samples may beintroduced to the analyzer at any time, even when the analyzer isalready in a running mode. In the clinical laboratory, it is sometimesnecessary for an assay to be run immediately on a particular patient'ssample. Such assays are referred to as STAT assays.

Examples of instruments that have batch access include the IMx SelectSystem, manufactured by Abbott Laboratories, and the ES 300 ImmunoassaySystem, manufactured by Boehringer Mannheim. In use, containers withsample liquids are placed on the transport circuit of these instrumentsin batches, and the containers travel in a fixed cycle so that eachcontainer passes through various operating stations in sequential order.In these instruments, all the sample containers must be processed beforenew samples are added. Some batch systems have means for assaying newsamples on a STAT basis. In such systems, however, STAT sampleintroduction and processing are delayed until all the samples already inthe assay process are completed.

Instruments that have continuous access of samples, as defined herein,include the IMMULITE™ Automated Immunoassay System manufactured byCirrus, the Affinity™ Immunoassay System, manufactured by BectonDickinson, the AIA-1200/AIS-600 Automated Immunoassay Analyzers,manufactured by TOSOH, the Immuno 1 Automated Immunoassay System,manufactured by Technicon, the System 7000 manufactured by Biotrol, andthe OPUS™ Immunoassay System, manufactured by PB Diagnostics.

Another feature that differs among the automated analyzers currentlyavailable is the capability of the system to analyze one sample formultiple analytes during any period of operation. Analyzers that cananalyze samples for two or more analytes, with two analysis methodsbeing performed by the instrument simultaneously, will be describedherein as having an "integrated mode of operation." Most of theautomated analyzers currently available include this feature althoughthe method in which the assays for multiple analytes are accomplisheddiffers significantly.

In the diagnostics industry, the term "random access" is sometimes usedto refer to the ability of an instrument to assay for any analyte on anysample at any time. It is desirable for all tests required on a sampleto be done on one instrument at one time. Many of the instruments thathave an integrated mode of operation purport to be "random access"instruments even though tests for certain analytes cannot be performedon some of the instruments because of limitations of the instrument'smode of operation.

Analyzers that have an integrated mode of operation can be furtherdivided into subcategories based upon the flexibility of the instrumentin handling the assay format requirements of various analytes. Someinstruments deal with all tests using the same basic protocol. Theamounts and type of reagents mixed with the sample may vary when testingfor various analytes, but the reaction incubation time or the processingsequence is fixed. In some single protocol analyzers the incubation timefor assay formats varies but only in multiples of the predeterminedincubation length.

The IMMULITE™ Automated Immunoassay System is an example of aninstrument having an integrated mode of operation but using a singleprotocol, although the incubation time for some analytes may be doubled.

Such single protocol instruments may assay for a broad menu of analytesbut typically the lack of flexibility in assay protocols availableresults in decreased throughput or in decreased sensitivity for certainanalytes.

Other automated analyzers with integrated modes of operation have agreater variation in assay protocol in terms of variations in incubationtime, and perhaps in wash steps, than the single protocol instrumentsdescribed above. For purposes of this description, such analyzers willbe referred to as "multiple protocol" analyzers.

Typically, in multiple protocol analyzers the sequence of protocol stepsvaries. For example, one assay protocol may require sample exposure toan assay constituent pipetting station, followed by an incubation stepand then detection of a labeled reagent at a reading station. Anotherassay protocol may require sample exposure to a reagent pipettingstation, followed by an incubation step, followed by a second exposureto the reagent pipetting station, a second incubation and finallydetection of a labeled reagent at a reading station. In this type ofinstrument, which is referred to herein as a "multiple chronology"instrument, the two assay protocols can be simultaneously processed.

The Affinity™ Immunoassay System is one example of an instrument whichis both multiple protocol and has multiple chronology processing. U.S.Pat. No. 4,678,752 describes the operational methods upon which thisinstrument is based in detail. The Affinity™ Immunoassay System includesmeans for transporting reagent packs in any order and in any directionas dictated by the assay protocol for a particular analyte.

Another feature which differs among known automated analyzers is themethod used to schedule the timing of the assay resources of theinstrument. The assay resources include sample pipetting, reagentpipetting, incubator transfer stations, wash stations, read stations andthe like. In any automated analyzer, some means must control thetransport of assay constituents, i.e., reagents and sample, from oneoperational station to the next and also control the timing of theoperations performed at such stations. The scheduling of such timing istypically controlled by a computer program.

One common method of scheduling assay resources is based upon the use ofa predetermined fixed cycle. As used herein, "predetermined fixed cycle"shall mean any method of scheduling the timing of assay resources sothat all the assay resources in the instrument operate within a fixedlength, predetermined cycle. Systems having this scheduling method willhave each assay resource returning to a predetermined location at theend of each cycle.

Known automated analyzers which have the predetermined fixed cyclemethod of scheduling the timing of resources also have single chronologyoperation. For example, both the IMMULITE™ Automated Immunoassay Systemand the ACS:180™ Automated Immunoassay System described have apredetermined fixed cycle method of scheduling resources. As describedabove, each container of sample proceeds through each of the operationalstations of the above analyzer in the same order. The Dade Stratus IIImmunoassay System is another such automated immunoassay system and isalso described in Volume 14 of the J. Clin. Immun. In the Stratusanalyzer reaction tabs are positioned around a generally circular wheel,with reaction tabs being disposed about the periphery of the wheel. Anincubation stage, a washing stage and a reading stage are positionedaround the periphery of the wheel. The wheel moves forward a fixeddistance for each cycle of the system, indexing sequentially in aclockwise fashion past these stages.

In a normal, single stage assay, the sample and the necessary reagentsare added at a pipetting location and the wheel begins to index forwardthrough the incubation stage. Since the wheel indexes a fixed distancefor each cycle of fixed duration, the incubation time for the sample ispredetermined for all samples. The reaction vessel then moves on to thewash and read stages according to a fixed time schedule and the spentreaction vessel is discarded.

If a particular assay protocol requires a longer incubation time, theonly option is to allow the sample to proceed through the wash and readstations and proceed back to the pipetting location without beingdiscarded. This sample must then make the entire trip back around thewheel before it can be read. Not only does this significantly limit theflexibility of the system, it also requires assay resources ( i.e., thewash and read stations and the pipetting location) to be dedicated tothe sample even though the sample does not require these resources toperform any function.

As discussed above some assay formats, require two stages of processing,each stage requiring the addition of reagents, incubation and washing,and only after the second stage does the sample proceed to a readingstep. In the known analyzers with predetermined fixed cycle methods ofcontrol, the assay constituents are transported in a vessel that cannotreverse direction and allow additional reagents, incubation, and washingsteps to be performed before reading occurs. Automated analyzers withpredetermined fixed cycle scheduling control currently available do notpermit flexibility in incubation times between assay formats. Althoughassay protocols may vary for each analyte, all incubation times aregenerally the same. When the incubation time does differ, it is always alonger incubation time and it is a multiple of the "normal" incubationtime for that analyzer. For example, in the ACS:180™ AutomatedImmunoassay System, the incubation time is doubled for certain analytes.This feature limits the availability of assay protocols on theanalyzers.

Another type of scheduling method used in automated analyzers does notuse a fixed cycle. This type of scheduling method will be referred to as"adaptive timing." Adaptive timing, as used herein, means that the assayresources are scheduled and controlled in such a way that the timing mayvary depending on the status of the analysis in process. For instance,the timing may vary based on a measured reaction parameter, e.g.reaching a predetermined threshold level or a predetermined signal rate.

Known automated analyzers that have a multiple protocol, multiplechronology processing format all have adaptive timing control of theassay resources. As described above, such analyzers differ from thesingle chronology processing, predetermined fixed cycle analyzers inthat their operation is much less rigidly time-dependent. In adaptivetiming analyzers, the timing of the addition of various reagents, theincubation time, and other time-dependent functions can be variedindividually for each assay. This greatly enhances the flexibility ofsuch analyzers. However, the information that must be accuratelyrecorded and tracked for each individual assay handled by the analyzergreatly increases the complexity of the control. The more assays beingprocessed in such an analyzer at any give time, the greater thedifficulties will be in accurately controlling the system to conduct thetest. Additionally, every test performed on the analyzer will requireits own specific reagents and processing times. By adding wider testcapabilities, the amount of information that must be handled by theanalyzer controller becomes that much more complex. The complexity ofthe control in such adaptive timing analyzers can significantly affectthe throughput of the system--as the complexity of the control systemincreases, the number of samples that the analyzer can process in agiven time decreases. Moreover, as the number of assay resourcesrequired for a particular protocol increases, the complexity of controlin an adaptive timing controlled analyzer increases.

Automated analyzers such as the Affinity™ Immunoassay System haveadaptive timing and use a complex scheduler program to handle themultiple protocols. As described in U.S. Pat. No. 4,678,752, thescheduler program of the instrument claimed therein examines all of theactions required to complete the processing of the samples currently inthe apparatus, and then arranges them into a sequence which attempts touse the capabilities of the apparatus efficiently. First, the schedulerdetermines whether any samples have been introduced to the analyzer, theprocessing of which must be scheduled. The scheduler prioritizes theprocessing of reagent packages with those samples, a schedule plan ismade and a scheduling order is arranged. Each new sample added to theanalyzer has its own schedule plan that is then fit into the schedulingorder.

It would be desirable to have an automated chemical analyzer that hadthe multiple protocol, multiple chronology processing and theflexibility provided thereby with the simplicity of the predeterminedfixed length cycle method of scheduling the assay resources.

SUMMARY OF THE INVENTION

The present invention provides methods and apparatuses that permit theclinical analysis of samples for multiple analytes with a variety ofassay protocols in a multiple chronology sequence while operating on apredetermined fixed length cycle method of timing control. This methodprovides unique flexibility and mechanical and control simplicity.

In one method of the invention, analyzer control means are providedcomprising scheduling means and transfer control means. A fixed cyclelength is predetermined for controlling certain assay resources locatedin assay resource stations and that information is provided to thescheduling means. These assay resources are generally an assayconstituent delivery means, an incubator belt, a wash means and signaldetection means. Each of the assay resources is assigned a fixedoperating sequence, that is a time period of fixed duration during whichthat assay resource is available to perform a predetermined operation ona sample-containing reaction vessel, that begins and ends within thetime cycle of predetermined length. Desirably, an operating sequencethat is a first indexing cycle having a first indexing time is assignedto one of the assay resources, such as the incubator. In a preferredembodiment, that first indexing time equals the fixed cycle lengthpredetermined for controlling the scheduling of assays. Each of theother assay resources is also assigned a fixed operating sequence, wherethe first indexing time is preferably an integral multiple of each suchoperating sequence so that the incubator and the other assay resourcesoperate synchronously with each other. Although the integral multiplemay be one, such that the first indexing time may be equal to the fixedsequence of the other assay resources, the two cycle times desirablydiffer from one another. In a preferred embodiment, the integralmultiple is three, i.e., the first indexing time of the incubation beltis three times as long as the operating sequence time of the other assayresources.

As noted above, known automatic analyzers that can process multipleprotocols using multiple chronology have very complex methods ofcontrolling the processing. A precise schedule for each and every sampleand reaction vessel must be stored and the controller must ensure that aspecific assay resource, such as a dispensing pipette, is available atthe precise time it is required.

In the method of this invention, each assay resource has a predeterminedfixed operation window within the fixed processing cycle. Resultingly,the control logic for one assay resource can rely on predeterminedtiming of other dependent and independent assay resources. Therefore,analyte tests having variable protocols and that are processed by movingreaction vessels in different chronologies can be interleaved if theirassay resource requirements do not conflict, i.e., analyte tests withshorter processing time can be entered after those with longerprocessing times and the shorter analyte test can finish first. This canbe done because the means of transporting reaction vessels containingassay constituents can present reaction vessels to the necessary assayresources in whatever order is required, regardless of entry order. In apreferred embodiment an optimizing routine is used by the analyzercontrol means for increased performance and throughput.

In an embodiment of the invention, variable dwell time in an assayresource station may be achieved for the various analyte test protocolsby using independent internal storage or by providing the reactionvessel transport means with excess capacity.

The method of the present invention greatly simplifies scheduling whilemaintaining a maximum degree of flexibility in the system. Whereas knownmultiple protocol, multiple chronology analyzers operate on a true timeline in a fashion analogous to analog electrical processing, the methodof the present invention schedules in terms of discrete time slots, morelike digital processing of electrical signals. Each time slot of theanalyzer as a whole is desirably equal to the first indexing time of theincubator belt. Thus, a reaction vessel can be transferred to the washwheel only at the beginning of the indexing cycle of the incubator.Because the a processing cycle is fixed, the indexing cycle of theincubator in the preferred embodiment, and the scheduling means matchesanalyte tests and assay resources within such a cycle, greatlysimplifying the scheduling.

Process control is also simpler in the method of the invention. Inadaptive timing analyzers, a resource must constantly monitor the statusof other dependent resources to determine the subsequent timing of itsactions. Analyzers controlled as described herein have time cycles offixed duration that can be relied upon by the scheduling means inensuring each assay resource will complete its operations within thepredetermined time without constantly polling the status of otherresources.

Interleaving of analyte tests with different protocols is not possiblewith known adaptive timing analyzers. Such analyzers control means mustfollow a first-in-first-out pattern of entering and processing the test,and an interruption of entry of a test results in a "hole" that consumesassay resources and increases the overall time required to process aworklist. In the method of the invention, the ability to interleaveanalyte tests makes it possible for the "hole" to be filled with anotheranalyte test having compatible assay resource requirements. The resultis shorter overall processing times for interrupted worklists or forsystems that receive intermittent analyte test entry.

In the analyzer of the invention, the dwell time of a reaction vesselcontaining assay constituents on the incubator belt is limited to a timeapproximately equal to an integral multiple of that first indexing time.In actuality, the actual time a vessel spends on the incubator belt maybe slightly less than a full integral multiple of the first indexingtime because it takes a short period of time after a reaction vessel istransferred to the wash wheel at the first wash transfer station beforethe incubator moves to the incubator transfer station to add a newvessel to the incubator. The use of a fixed cycle of predeterminedlength limits the "chronological resolution" (i.e., the accuracy withwhich a given time can be varied) that may achieved in controlling thedwell time of a vessel in the incubator. Specifically, the analyte testmust be based on a protocol where the incubation time will fall within arange of incubation times within one half the first indexing time. (Forexample, if the first indexing time is 36 seconds, the incubation timesof the protocols would be variable within ±18 sec). This slightvariability in incubation time does not, however, result in loss ofprecision, thus ensuring that the test results are reproducible.

In use, an apparatus of the invention transports reaction vesselscontaining the assay constituents for a particular analyte test to thevarious assay resource stations where assay resources associated withthe station are capable of performing one or more predeterminedoperations on the reaction vessels during the fixed time slot ofavailability assigned to such assay resource. For example, the assayconstituent delivery means delivers predetermined amounts of sample andreagents to the vessel. The incubator belt may transfer a reactionvessel along a predetermined path in the incubator. In the wash station,assay resources act upon the reaction vessel by transporting the vesselto one or more positions in the apparatus, where labeled reagents boundto a solid phase are separated from unbound labeled reagents and bufferis dispensed and aspirated from the reaction vessel. In the readstation, assay resources act upon a reaction vessel by transporting thevessel first to a position in the apparatus where reagents required toprovide a detectable signal will be added and then to a signal detectionmeans, a luminometer in the preferred embodiment of this invention,where signal is detected and recorded by the apparatus.

One embodiment of an apparatus of this invention includes the followingpredetermined assay resources: assay constituent delivery means, anincubator belt, separation and wash means and means for detecting asignal. The apparatus will also include means for transporting areaction vessel from one resource to another and analyzer control meansdescribed above. A particularly preferred embodiment includes as anassay resource a vessel chain positioned in the apparatus so that assayconstituents may be added to a reaction vessel while the vessel is onthe vessel chain before the vessel is transferred to another assayresource so that transport of other reaction vessels is not delayedduring the delivery process.

The wash station is preferably physically integrated with the readstation along a continuous, endless path on a wash wheel. This physicalintegration of the two stations, combined with the mechanical simplicityof the transfer stations, reduces the mechanical complexity of theanalyzer of the invention over other analyzers known in the art; suchsystems generally require complex transfer mechanisms having separatemotors and the like for transferring vessels from one stage ofprocessing to another or the vessels follow only a single path and mustproceed sequentially through each operational station. Mechanicalsimplicity increases the reliability of the analyzer of the invention byreducing the number and complexity of moving parts in the analyzer.Another advantage provided by the physical integration of the read andwash station is that the entire analyzer can be very compact. In apreferred embodiment, the wash wheel, incubator belt and assayconstituent supply wheel are all arranged with respect to each other andwith respect to the electronics and fluidics of the analyzer so thatevery assay resource can be accessed by an operator from a singlestationary position in front of the analyzer.

Even though the wash and read stations are physically integrated, theyare logically separate, i.e., separately controllable by the analyzercontrol means.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an analyzer of the invention;

FIG. 2 is a perspective isolation view of a portion of the analyzer ofFIG. 1 showing a portion of the vessel chain and a portion of theincubator belt and the interaction therebetween;

FIG. 3 is a perspective isolation view of a portion of the analyzer ofFIG. 1 showing a portion of the incubator belt and the wash wheel andthe interaction therebetween;

FIGS. 4-8 are schematic, perspective views of a portion of the analyzerof FIG. 1, showing transfer positions between the incubator belt, thewash wheel, and the read station;

FIGS. 9 and 10 are flowcharts depicting the scheduling logic of anembodiment of the invention for one-stage and two stage assays,respectively;

FIG. 11 is a schematic representation of a time-dependent assay resourceavailability schedule for a series of assays performed on an analyzer ofthe invention; and

FIGS. 12A and 12B are portions of a timing diagram of operationsoccurring on the analyzer of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically represents an analyzer 10 of the invention. Theanalyzer shown includes an assay constituents supply wheel 20, an assayconstituents delivery means 40, an incubator 50, a wash wheel 60positioned adjacent a wash station 100 and a read station 130 andvarious other components that will be described below.

The assay constituents supply wheel 20 rotates in a generally horizontalplane and includes an annular outer carousel 22 for receiving a seriesof samples, samples may be patient specimens, controls or calibrators,and an inner carousel 30 for storing a plurality of reagent packs 32.Each sample is preferably provided in a sample cup 24 adapted to besafely and securely received on the outer carousel 22. A plurality ofthese sample cups is provided on this annular carousel so that a samplemay be placed in the analyzer at the operator's convenience.

Although FIG. 1 depicts the outer carousel 22 as comprising only arelatively short arc, the outer carousel preferably extends about theentire periphery of the supply wheel 20. In one preferred embodiment,sample cup container trays may be included which are designed in a shortarc and which are adapted to fit on the outer carousel of the supplywheel. The container trays desirably are designed to receive a pluralityof sample cups and a plurality of these trays may be positioned aboutthe periphery of the supply wheel. In a preferred embodiment, thesetrays are independently removable, permitting batches of sample cups tobe swapped out of the analyzer in a single step. The sample trays aredesirably designed to support use of containers of a variety of shapes.For example, the sample tray of the analyzer shown will support samplecups designed for the tray, 13×75 mm or 13×100 mm test tubes, and 13×75mm or 13/100 mm serum separator test tubes.

Once the operator has placed patient sample in a sample cup on theanalyzer, the operator must provide analyzer control means withinformation identifying the sample and the analyte test to be performedon the sample. This information must include the position of the samplecup on the apparatus. The operator may manually enter the identifyinginformation about a sample or the information may be provided on thesample cup with a label readable by the analyzer, such as a bar codelabel. A bar code reader 26 may be included in the analyzer for thispurpose.

Reagent packs 32 are designed to be positioned on the inner carousel 30of the supply wheel. Each pack desirably includes a plurality ofdiscrete wells 34 in which a quantity of a given reagent may be stored.Preferably, each reagent pack is analyte-specific and provides asufficient quantity of each reagent necessary to process at least oneanalyte test. The packs desirably include a sufficient quantity of eachreagent to conduct a number of analyte tests on different patientsamples. When the reagents in a pack are exhausted the operator removesthe pack and replaces it with a new one. The inner carousel 30 of theassay constituents supply wheel may be refrigerated to maintain reagentsstored in the apparatus at refrigeration temperatures, 4°-10° C.,increasing reagent shelf-life and stability. Information regarding theposition and contents of each reagent pack 34 may be provided to theanalyzer control means using a label readable by the analyzer. Suchinformation may include reagent pack test name, lot number, expirationdate and the like. As with the sample cups, the label is preferably abar code label that may be read by a reader included in the apparatus orby a wand type bar code reader. The information on the label may also beentered manually.

The analyzer shown in FIG. 1 begins processing an analyte by using assayconstituents delivery means 40 to withdraw a predetermined amount ofpatient sample from a sample cup and transfer it to a reaction vesselheld elsewhere in the apparatus. In a preferred embodiment, the deliverymeans includes a probe 42 that has an ultrasonically activatable tip(not shown) and a pump (not shown). Ultrasonic vibrations generated byan ultrasonic transducer may be applied to the probe tip to mix fluidsin the reaction vessel, sample cup or reagent pack wells before or afteraspiration, to clean the probe after each use, and for liquid levelsensing. Assay constituents delivery means useful in automated analyzersand ultrasonic probes are well known and will not be described in detailhere. The probe may include means for heating the liquid it withdrawsfrom a vessel. This feature allows the liquid to be preheated to theincubation temperature before it is dispensed into a reaction vessel. Ina preferred embodiment the pump is a dual-resolution diluter pump, suchas the pump described in U.S. Pat. No. 4,941,808. This pump permitsaccurate and precise delivery of both large and small fluid volumes. Thepump delivers wash buffer to the prove for washing and sample dilutions.It also aspirates samples and reagents into the probe for delivery intoreaction vessels.

As indicated schematically in FIG. 1, the assay constituents deliverymeans 40 is adapted to access a sample cup 24 containing a patientsample, a reaction vessel 52 and each of the wells 34 of a selectedreagent pack. In FIG. 1, the assay constituents delivery means isrepresented as a single probe 42. If desired, a plurality of probes maybe employed, e.g., with one probe dedicated to transferring patientsample and one or more probes used to transfer reagents.

In the analyzer shown in FIG. 1, the probe 42 is carried on a track 46.This permits the probe to move laterally from an aspirating positionover a sample cup or a reagent well to a dispensing position (as shown),where the aspirated liquids may be dispensed into a reaction vessel. Theinner and outer carousels (30 and 22, respectively) of the supply wheelare independently rotatable about their axis so that any desired patientsample and any desired reagent pack can be independently positioned foraccess.

In a preferred embodiment, the reagent packs are covered with aresealable material that may be pierced by the probe tip but which willsubstantially reseal as the tip is withdrawn.

Once a predetermined amount of patient sample is dispensed into areaction vessel, the reagent or reagents necessary for the specifiedtest are added to the reaction vessel. In a preferred embodiment,magnetic or paramagnetic particles are used as a solid support.Alternatively, of course, beads or the tube walls may be coated and usedas a solid support utilizing known procedures. When the magneticparticles are used, each reagent pack 32 contains magnetic particleswhich may be coated with an assay-specific reagent or which may becoated with a generic reagent. The particles are stored in the reagentpack in a buffer solution. Desirably, before the predetermined amount ofbuffer-particle solution is withdrawn from the reagent pack, thesolution is mixed by some means. In one embodiment, the ultrasonic probeis vibrated to mix the fluid to uniformly suspend the particles.Alternatively, the apparatus could include means for vortexing theliquid in the well or means for stirring the liquid using a stirringbar.

The analyzer shown in FIG. 1 includes a probe washing station 44. Inorder to avoid cross-contamination between patient samples or betweenpatient samples and reagent supplies, after the probe of the assayconstituents delivery means has dispensed a quantity of liquid, itshould be cleansed. In the preferred analyzer, the probe washing station44 includes a toroidal fluid delivery band 45 carried on the inner wallsof a drain cup 46 positioned beneath the band 45. The fluid deliveryband 45 is arranged to be coaxial with the probe tip and the probe tipmay be inserted through the band. The fluid delivery band comprises atubular component having ports spaced circumferentially about the bandsurface that face generally radially inwardly toward the probe tip. Theband should be of a sufficient diameter so that when the probe tip isinserted, the outer surfaces of the probe do not touch the walls of theband. The band diameter should, however, be small enough so that fluidmay flow through the ports and wet the outer probe surface to cleanseit. The inner probe surface is desirably cleansed by flowing a quantityof a wash or cleansing solution through it. The drain cup 46 is arrangedto receive probe cleansing solution and conduct that fluid to a wastecontainer (not shown).

In a preferred analyzer the probe washing station further includesdrying means that draws air and cleaning solution through the band intothe drain cup and about the outer surface of the probe to pull excessliquid from the probe surface. When a ultrasonic probe is used, theprobe is desirably ultrasonically activated for a sufficient period oftime to atomize fluid on the surface of the probe, to aid in drying theprobe.

During the sample and reagent dispensing steps, the reaction vessel maybe positioned on the incubator belt 54 of the incubator 50. In such anembodiment, however, the incubator belt would have to remain essentiallystationary during the liquid dispensing cycle, thus delaying thetransport of other reaction vessels by the incubator belt. To avoid thisdelay, a preferred embodiment of the analyzer includes an assayconstituent dispensing station 55 (FIG. 2) that includes a vessel chain70 positioned off the incubator belt 54. The vessel chain 70 isdesirably adapted to carry a plurality of vessels along its length. Thevessel chain 70 desirably includes a floor 73 for supporting the bottomof a reaction vessel, a series of parallel, spaced-apart fingers 71 forsupporting diametrically opposed sides of the vessel and parallel meansfor supporting the other opposing sides of the vessel to hold the vesselin a generally vertical position. The parallel means may include asupporting wall 74 on one side and an empty vessel from the new vesselloader 72 (FIG. 1) on the other side. The new vessel loader 72 isprovided adjacent the vessel chain 70 to supply new reaction vessels tothe analyzer. The new vessel loader is readily accessible to an operatorto permit the operator to add additional reaction vessels to the supplyas the analyzer disposes of used reaction vessels.

The new vessel loader 72 desirably presents a series of essentiallyparallel lines of new vessel to the chain 70, with the lines beingspaced to position a new vessel in each line immediately adjacent avessel carrying position on the vessel chain. The new vessel loadershown includes a series of parallel supporting walls 79 spaced to allowa vessel to slide between them while supporting the vessel in agenerally vertical position. Each row of empty vessels is urged forwardby a substantially vertical finger (not shown) that is slidably mountedin the floor of each row and supports the outermost (i.e., closest tothe bottom in FIG. 1) empty vessel of each row. In the event no emptyvessels are present in a row of the new vessel loader, the verticalfinger will support a reaction vessel on the vessel chain 70.

In the embodiment shown in FIGS. 1 and 2, the vessel chain intersectsthe incubator belt 54 at the incubation transfer station 160 andcontinues to a vessel disposal station 162. At the incubation transferstation 160 the reaction vessel may be transferred to or from theincubator belt or it may be transported to the vessel disposal station.In a preferred embodiment, the vessel accessed by the probe 42 duringany operating cycle of the analyzer is spaced two positions away fromthe incubation transfer station. When all the necessary fluids have beenadded to that vessel, the vessel chain will be moved forward (to theright in FIG. 1) two positions, positioning that vessel at theincubation transfer station. After the vessel is removed from the vesselchain, as described in detail below, the vessel chain will be retracted(to the left in FIG. 1), placing a new vessel in position for access bythe probe. In most analyses, the vessel chain will be retracted only oneposition.

Some assay protocols require "two-stage" processing, where additionalreagents must be added to a reaction vessel after a first incubation andwashing process. When a reaction vessel requires such additional reagentaddition steps, the vessel chain may be retracted two positions, ratherthan one. First, sample and reagents are added to an empty reactionvessel, that reaction vessel is moved forward two positions to theincubation transfer station 160, and that vessel is transferred onto theincubator belt. Before the vessel chain retracts, the reaction vesselrequiring additional reagent is positioned at the incubation transferstation. The chain is retracted two positions, transferring the vesselto the chain and positioning it at the probe's dispensing position.After additional reagent has been added to that reaction vessel, thevessel chains moves the vessel forward two positions back to theincubation transfer station for transfer onto the belt.

When all the new vessels on the chain are used, the chain is positionedadjacent the vessel supply and all of the lines of vessels in the newvessel loader 72 will be indexed forward one position by urging thevessels in line forward about the width of one vessel. This will add onenew vessel to the chain from each line of vessels, providing a series ofnew vessels on the chain for use. Once those vessels have been used, theprocess may be repeated.

The vessel chain may be of any useful configuration, and the incubationtransfer station may be of any type. In a preferred embodiment, however,vessels will transfer from the vessel chain to the incubator belt in thesame manner in which vessels are transferred to and from the wash wheelwhich is described in detail below.

The incubator 50 desirably has an incubator belt 54 which is designed totransport one or more reaction vessels in any direction along apredetermined path 58. Although the schematic depiction of FIG. 1 showsreaction vessels only along a portion of the circumference of theincubator, the incubator desirably is adapted to carry vessels along itsentire circumference. The reaction vessels are adapted for movementtogether within the incubator, but they should be relatively easilyplaced onto or removed from the belt. In one preferred embodimentdescribed below in connection with FIGS. 3-9, the belt 54 is adapted toreleasably receive and engage each of the vessels for movementtherewith.

The incubator desirably includes a housing which includes a pair ofparallel walls 56 which are spaced apart from one another to define theincubator path 58. The incubator also includes a floor 57 for supportingthe bottom of the reaction vessels 52 and means for controllingtemperature. The incubator is desirably maintained at a uniform,elevated temperature to ensure reproducibility of test results and tooptimize reaction kinetics. Desirably, the temperature of the reactionmixtures in the reaction vessels is maintained at about 37° C.±1° C. Ina preferred embodiment, the parallel walls 56 of the incubator aremaintained at the desired temperature and heat the reaction vessels andtheir contents by convection. In order to assure uniformity oftemperature along the length of these walls, they should be formed of amaterial which conducts heat rapidly, with aluminum being particularlypreferred. Preheating sample liquid or reagents using the probe of theassay constituents delivery means before dispensing them into thereaction vessels will help to assure a uniform temperature is maintainedwithin the reaction vessel.

The incubator belt shown as 54 in FIG. 2 comprises an elongate, endlesstape 62 which extends along the entire length of the incubation path 58at a position disposed generally above the floor 57 of the incubator.This tape should be flexible so that it may travel around the corners ofthe incubation path. The tape is adapted to carry a series ofspaced-apart carriers 64 along its length. Each carrier includes aconnector 66 for connecting the carrier to the tape 62. The carriers maybe removably attached to the tape so that they can be easily replacedwithout having to replace the entire incubator belt 54.

The carrier 64 also includes a pair of spaced, parallel fingers 68 whichdepend downwardly from the connector 66. These fingers are spaced apartfrom one another a distance slightly greater than the width of areaction vessel 52 so that a reaction vessel may pass between thefingers without undue resistance. The spacing between the fingers shouldnot be too great, however, because the fingers are positioned to helpsupport a reaction vessel in a generally vertical position, as shown.The parallel walls 56 of the incubator are desirably similarly spaced toprovide additional support to the reaction vessels. Each reaction vessel52 rests upon the floor 57 of the incubator, and the parallel fingers 68of the incubator belt carrier and the parallel walls 56 support thevessel in a generally vertical position as it is moved along theincubation path.

The carriers 64 of the incubator belt are desirably spaced apart fromone another along the length of the tape 62 to form a space 65 betweenadjacent fingers 68 of adjacent carriers 66. This space 65 should besufficiently wide so that a reaction vessel may freely pass throughwithout having its progress obstructed, but narrow enough so that thecarrier fingers can support a reaction vessel in a generally verticalposition. These spaces 65 will be referred to as "empty" positions andare desirably alternately positioned with respect to carrier positionsalong the entire length of the belt.

Another assay resource of an analyzer of this invention is the washstation 100. As mentioned above, in a preferred embodiment, the washstation and the read station is each positioned in the analyzer in amanner such that reaction vessels will be transported along apredetermined path and at predetermined positions along that path thereaction vessels will be acted upon by the wash station and/or the readstation. As shown in FIG. 4, the reaction vessels are transported alongthis predetermined path 101 by a rotating component 102, which will bereferred to as the wash wheel. The wash wheel (FIG. 3) includes a floor104 for supporting the bottom of a reaction vessel, a series ofparallel, spaced-apart fingers 103 for supporting diametrically opposedsides of the vessel and parallel walls 108 for supporting the otheropposing sides of the vessel. As in the incubator, the walls may beheated to maintain a substantially constant, elevated temperature ifdesired.

Unlike the incubator belt which is adapted to receive a vessel only atalternating positions along the belt, the wash wheel is desirablyadapted to receive a vessel between each set of fingers along its path.This may be accomplished by providing equal spacing between the fingers103 along the wash wheel path rather than using an uneven spacing formatsuch as is used along the length of the incubator belt. Additionally,where the fingers 68 of the incubator belt depend downwardly, thefingers 103 of the wash wheel are attached to the floor 104 and extendgenerally vertically upwardly. The floor and the fingers are adapted tomove together to move vessels along the wash wheel path. This may beaccomplished by the floor being fixed in place on the wheel so that thefingers move as the wheel turns. Alternately, the floor may moveindependently of the wheel, the wheel desirably being fixed in place,and the fingers could be attached to the floor so that when it movesreaction vessels carried by the fingers will be transported along thepath. Although the floor 104 may be flexible so that it may follow acomplicated path, in a preferred embodiment the wash wheel is round andthe floor is a rigid annular ring. If so desired, the upwardly extendingfingers 103 may be integrally formed with the floor 104.

In a particularly preferred embodiment of the invention, the analyzer ofthe invention includes a novel method of moving reaction vessels betweentwo transport mechanisms. In this embodiment the transport mechanismsare the transport means that are adapted to move reaction vessels alongthe wash wheel and incubation paths. Desirably the wash wheel path andthe incubation path intersect at two transfer stations. FIG. 3 is apartially broken-away view of the first wash transfer station 80. Atthis transfer station, the incubator belt 54 and the wash wheel path 101overlap permitting a vessel to be transferred from the incubator to thewash wheel. As shown in FIG. 3, when a vessel is ready to betransferred, the wash wheel will be positioned with respect to theincubator belt so that a pair of the wash wheel fingers 103 are disposedadjacent opposite sides of the floor 57 of the incubator and generallybetween two fingers 68 of the incubator.

It should be noted that the wall 56 of the incubator has been brokenaway in this view to show the overlap between the wash wheel path andthe incubator path. In actuality, the gap in the wall 56 through whichthe wash wheel fingers pass is only slightly wider than the floor of thewash wheel. This permits opposing sides of a vessel on the incubator tobe continuously supported as it moves along the incubation path onto thewash wheel floor, either by the walls 56 of the incubator or the fingers103 of the wash wheel.

As mentioned above, although in the embodiment shown the read and washstations are both positioned along the endless path of a wash wheel, theread and wash stations may each be positioned elsewhere in theapparatus. For example, the wash station may be positioned adjacent onewheel and the read station may be independently positioned adjacent asecond wheel. Reaction vessels transported by the incubator belt 54could be transferred to the wash and read stations on the separatewheels by any known means, such as a mechanical arm which will lift thevessel from one belt and place it on another belt.

In the preferred embodiment shown, both stations are positioned alongone path and on one wheel, thus decreasing the number of transfersnecessary during an assay.

Referring to FIGS. 3 and 4, when a reaction vessel 52 containing assayconstituents on the incubator belt has completed its incubation, thevessel is positioned for transfer to the wash wheel. Moving theincubator belt 54 positions a carrier 64 carrying the vessel at thefirst wash transfer station 80. This disposes the vessel between twoparallel fingers 103 of the wash wheel and onto the floor 104 of thewash wheel. The floor 104 of the wash wheel is desirably substantiallyaligned with the floor 57 of the incubator in order to permit the smoothpassage of a vessel through the first wash transfer station.

The wash wheel may then be indexed forward one position (i.e., movedclockwise as shown in FIGS. 4-8) to the position shown in FIG. 5. Sincethe fingers 103 of the wash wheel are oriented generally perpendicularlyto the fingers 68 of the carrier at the first wash transfer station, thevessel will move with the wash wheel rather than remain in the carrier,therefore exiting the incubator and being transferred to the wash wheel.This leaves the carrier at the first wash transfer station empty.

A reaction vessel 52' containing a sample for which testing is completedand the detectable signal measured at the read station 130 is ready forremoval from the analyzer. That vessel will be moved into the positionon the wash wheel immediately preceding the first wash transfer station,as shown in FIG. 4. When the wash wheel indexes to move reaction vessel52 from the incubator belt, the used reaction vessel 52' will move intothe position previously occupied by the other reaction vessel 52 andinto the empty carrier of the incubator belt.

As shown in FIG. 6, the incubator belt is then indexed forward until anempty position 65 of the belt is positioned at the transfer station, andtransferring the used reaction vessel 52' onto the incubator belt. Afterthe used reaction vessel is transferred onto the incubator belt it iscarried by the incubator belt to the incubation transfer station. Whenthe vessel chain moves a vessel forward two positions, the used reactionvessel is transferred onto the vessel chain which becomes the vesseldisposal chain. As the vessel chain is moved forward and back the usedreaction vessel is transported to the waste chute 162. This waste chuteleads to a waste collection container 164, where a number of usedvessels may accumulate for later disposal. Although this wastecollection container may take any desired form, it is preferred that itbe of the type commonly used for medical waste. Preferably the containeris provided with means for allowing a spent reaction vessel to enter thecontainer while preventing the inadvertent withdrawal or removal of thevessel. The used vessel may be ejected from the vessel chain onto thechute 162 by a separate mechanism, such as the turnstile 166 shown inFIG. 1.

Referring again to FIGS. 4-8, the wash-cycle path 101 extends from thefirst wash transfer station 80 to a second wash transfer station 120. Awash station is desirably positioned adjacent the path 101. The washstation in this embodiment includes six locations where the reactionvessel may be acted upon. When a vessel is transferred onto the washwheel at the first wash transfer station 80 it is indexed forwardthrough the wash cycle which in this embodiment includes a plurality ofpositions where the vessel is acted upon. In a preferred embodiment, ifa wash and separation step is required at all for a particular assay thefollowing occurs as the reaction vessel is indexed ahead one positionduring every cycle of the wash wheel. At the first position followingthe first wash transfer station 80, liquid dispensing means (not shown)add a predetermined amount of wash solution to the reaction vessel andthe contents of the vessel. The reaction vessel is then indexed forwardto a position on the wash cycle having a pair of magnets (not shown)mounted on opposing walls of the wash-cycle path which cause themagnetic particles to be pulled from solution. Aspirating means (notshown) at this position along the wash-cycle path then withdraw theliquid from the reaction vessel. In the embodiment of the inventiondescribed here, the reaction vessel is indexed forward through a totalof six positions, three positions where wash solution is added andmixing occurs alternating with three magnetic separation-aspirationpositions.

Liquid dispensing means useful with this invention include any probe orpipetting means known in the art. In this embodiment, the liquiddispensing means includes three probes or tubular pieces, each probebeing capable of moving downwardly into a reaction vessel so that apredetermined amount of liquid may be dispensed therein. The probes areattached to a source of wash solution and in a preferred embodiment thethree probes are mounted on a carrier (not shown) that will move theprobes downwardly simultaneously. Thus, in the preferred embodimentthree reaction vessels may be washed simultaneously. The aspiratingmeans of this embodiment is similarly constructed.

Desirably while at the position where wash solution is added to thevessel, the contents of the vessel are mixed. In the embodiment of theinvention described here, mixing is accomplished as a spinning means(not shown) descends to the vessel and is releasably attached to theopening at the top of the vessel. The spinning means spin the vessel inone direction and then the other direction to suspend the particles inthe wash solution. Other mixing means are well known in the art. Forexample, a mixer may be attached to the liquid dispensing means androtated to mix the vessel contents, or the liquid dispensing means maybe a ultrasonic probe such as that described above.

As shown in FIG. 6, when an empty position 65 is located at the firstwash transfer station, a carrier 64 is located at the second washtransfer station 120. During the next cycle, the wash wheel is indexedforward (clockwise) one position, so that a washed reaction vessel 52"is positioned in an incubator belt carrier 64 at the second washtransfer station. The configuration of the second wash transfer stationis essentially identical to that shown in FIG. 3 for the first washtransfer station. Accordingly, a vessel may be transferred from the washwheel back onto the incubator at the second wash transfer station byindexing the incubator belt forward during the next cycle. The indexingof the wash wheel and incubator belt is controlled in accordance with amethod of the invention which will be described in detail below.

If the read station were physically separated from the wash station, thevessel would always be transferred either to the incubator belt from thesecond wash transfer station or directly to a belt or conveying devicewhich would transport the reaction vessel to the read station. In thepreferred embodiment of the invention, the read station is positionedalong the wash wheel path and physically integrated with the wash wheel102, as explained below. Accordingly, when a reaction vessel containingassay constituents has completed all of the necessary incubating andwashing steps, it may remain on the wash wheel and proceed through thesecond transfer station to the read station, as shown in FIG. 8. Thismay be accomplished by keeping the incubator belt stationary until thewash wheel goes through another indexing cycle and advances one moreposition. The vessel will then simply pass through the stationarycarrier at the transfer station without leaving the wash wheel. Even ifthe incubator belt must be moved between movements of the wash wheel,such as to carry out other operations, the same result can be achievedby repositioning the washed reaction vessel 52" back at the second washtransfer station before the wash wheel indexes again.

As previously noted, in some analyte tests, the protocol requires a washstep and then the addition of additional reagents or a dilution stepbefore a second stage of processing. In such a case, the incubator belt54 may be moved when the system is in the position shown in FIG. 7 totransfer the washed vessel 52" to the incubator belt. The incubator beltshould be moved to position the vessel 52" at the incubator transferstation 160 so it can be transferred onto the vessel chain 70 for theaddition of various reagents. An empty carrier 64 should then bepositioned at the second wash transfer station before the wash wheelindexes forward to ensure that a vessel will not be prematurelytransferred to the read station.

One other instance when it may be desirable to transfer a reactionvessel which has been washed back to the incubator at the second washtransfer station is when the sample needs a longer incubation periodafter the wash step than is permitted along the wash-cycle path 101. Asexplained before, the wash wheel moves in a lock-step fashion,preventing any significant variation in the time parameter of thewashing or reading functions.

When a reaction vessel is carried through the second wash transferstation to the read station a substrate addition station may bepositioned along the path so that substrate necessary to cause the assayconstituents to yield a detectable signal may be added. Some forms ofdetectable signal do not require the addition of a substrate; theanalyzer could, for example, be adapted to detect a fluorescent orradioactive label. In the preferred analyzer, the detectable signal isbased upon chemiluminescence. Accordingly, substrate for the generationof a luminescent signal in an enzyme assay must be added. In thepreferred analyzer shown in FIG. 1, substrate is added to the reactionvessel by means of a substrate pump (not shown). A suitable substrate issupplied to the pump and the pump may be adapted to dispense apredetermined volume of substrate into the reaction vessel.

Substrate reactions for producing a chemiluminescent signal generallyrequire that the substrate and assay constituents be maintained at arelatively constant, elevated temperature. It is preferred, therefore,that the walls 136 of the portion of the wash wheel adjacent the readstation be maintained at a constant, elevated temperature. The substrateaddition station desirably includes a substrate dispensing means, suchas a probe, that is heated so that the substrate added to the reactionvessel is heated to the appropriate temperature.

As shown in the figures, the read station 130 comprises alight-detecting means 140, e.g., a photomultiplier, positioned along thewash wheel path at a position adjacent the first wash transfer station80.

The light detector may be a photomultiplier tube designed to detect aspecific desired wavelength of light. When a vessel containing assayconstituents is located on the wash wheel immediately adjacent thephotomultiplier tube, the tube can monitor the luminescence of the assayconstituents for a predetermined period of time to detect a specificwavelength of light being emitted. The signal detected by thephotomultiplier tube is desirably conveyed to the controller 200 to beeither printed out for the user or further processed by the controller.The controller desirably includes a series of analyte-specificcalibration curves for correlating the measured luminescence of theassay constituents to the quantity of analyte originally in the patientsample. This signal may then be delivered to the operator as a finaltest result. If so desired, the controller may be programmed toreconduct the desired test on a particular sample by diluting thepatient sample if the signal generated by the sample is too great toprovide a reliable test result, such as when the detected signal is offthe scale of the calibration curve.

Once the assay constituents of a reaction vessel have moved through theread station, the vessel is indexed forward to the first wash transferstation. As explained above, the vessel may then be transferred to theincubator belt and moved to the incubator transfer station where it istransferred to the vessel chain for disposal. When the wash wheel isindexed forward three times as shown in FIG. 8, a reaction vessel on theincubator belt that has completed its incubation may be positioned atthe first wash transfer station, as shown in FIG. 4. This final movementof the incubator belt completes one full indexing cycle of theincubator. During this same period of time the wash wheel has indexedforward three times, i.e., completes three of its indexing cycles.

In the novel method of automatically analyzing samples of thisinvention, only one reaction vessel containing assay constituents may betransferred from the incubator to the wash wheel during an indexingcycle of the incubator. Accordingly, one reaction vessel is positionedin every third position of the wash wheel, with the intervening washwheel positions desirably remaining empty. This, in turn, dictatescertain geometrical spacing requirements of the analyzer.

The incubator should be configured such that the distance along theincubation path between the first and second wash transfer stations isequal to an odd number of positions along the incubator belt. Statedanother way, if one pitch of the incubator belt is defined as thedistance between one carrier and the next adjacent carrier, the distancebetween the first and second transfer stations should be m+1/2 pitches,wherein m is an integer. This ensures that whenever an empty position 65is at the first wash transfer station, a carrier will be positioned atthe second wash transfer station, and vice versa. This permits the washwheel to move as described above without prematurely transferring avessel from the incubator to the wash wheel path or inadvertentlytransferring a vessel from the incubator to the wash wheel path leadingto the read station. If the spacing differs, either the wash wheel orthe incubator belt could fail to align properly at the wash transferstations at the proper time, preventing one or the other from moving.Alternatively, the apparatus could position a carrier 64 at both of thetransfer stations at the same time mechanically, but that would preventthe maximization of resource utilization obtained when all of thecarriers carry a vessel for incubation.

The number of positions on the wash wheel and the number of thosepositions that lie along the portion of the wash wheel path that passesthrough the wash station can vary quite widely. The number of positionswill depend upon the number of functions that are to be performed onreaction vessels along that portion of the path as well as the dwelltime necessary for vessels moving along the portion of the path thatpasses through the read station. The relative proportions of the washportion of the path and the read portion of the path need not be thoseshown in FIGS. 4-8.

Regardless of the overall number of positions on the wash wheel and thenumber of those positions that are on the wash portion of the path orthe read portion, the total number of positions on the wash wheel andalong the wash portion of the path must be a multiple of three plus oneadditional position (3n+1), if, as here, the incubator belt's indexingtime is 3 times as long as the wash wheel indexing time. It should beunderstood though that if the indexing time of the incubator belt isincreased such as to 4, 5 or more that the multiple used to determinethe number of positions on the wash wheel must be similarly changed. Forinstance, if the indexing time of the incubator belt is 4 times the washwheel indexing time, the formula for determining the number of positionsshould be (4n+1). In the analyzer shown in FIGS. 4-8, there are 55(18×3)+1! positions along the length of the wash wheel, with 19 (6×3)+1! positions being disposed between the first and second wash transferstations. Although the embodiment of the invention described hereinshows the relationship between the wash wheel transport means and theincubator belt transport means, this method of transferring vesselsbetween two transport mechanisms can be used in other embodiments wherematerials must be transferred between two such mechanisms.

In order for the desired interaction of the incubator belt and the washwheel at the first and second wash transfer stations to occur, thenumber of positions on the wash wheel must be one position greater thana multiple of three positions. Referring to FIG. 5, a used reactionvessel 52' is positioned for transfer back to the incubator belt. Inorder for this transfer to take place, the incubator belt must be freeto move. If the number of locations were an integral multiple of three,the washed reaction vessel 52" would be at the second wash transferlocation and disposed at an empty position 65 on the incubator belt.When the incubator belt moved to remove the used reaction vessel 52',the washed reaction vessel 52" would be transferred to the incubatorpath at that empty position 65. By adding one additional position to thewash wheel, the incubator is free to move into the position shown inFIG. 6 and the wash wheel may then be indexed to transfer the washedreaction vessel 52" to the incubator belt, as shown in FIG. 7.

As mentioned above, the analyzer and method of the invention are basedupon a unique scheduling and timing method implemented by analyzercontrol means. In use, once a reaction vessel is filled with assayconstituents, the reaction vessel will transfer onto the incubator whereit will remain for a predetermined number of indexing cycles. The numberof cycles will be analyte test-specific and readily varied from one testprotocol to another. In the preferred embodiment, each indexing cyclelasts for the indexing time and the desired incubation time of the testprotocol can be expressed as a multiple of that time. Once the reactionvessel containing assay constituents has been incubated for thespecified time, the analyzer control means causes it to move to thefirst wash transfer station 80 for transfer to the wash wheel 100. Theanalyzer control means then cause the wash station to act on thereaction vessel as it is moved along the wash-cycle path, where thefunctions are timed on a cycle-by-cycle basis.

The analyzer control means comprises transfer control means, andscheduling means each of which comprises a computer program or asubroutine of a computer program, associated electronics and means ofconnecting the operative elements of the analyzer to the control means.The computer programs and the associated computer functions are includedin the electronics of the analyzer and generally include amicroprocessor, a hard disk and a floppy disk drive. The analyzercontrol means provides an interface into the apparatus through which itis possible to define the operations required to process a sample of anyparticular chemistry type and in any chronology. Assay data may bestored in data files of the computer program on the hard disk and maybe. subsequently retrieved for performing the desired assay. The storeddata, includes the mechanical assay requirements such as the control ofelectromechanical devices, the timing requirements of those devices,reagent package location and other such requirements. In addition tostored data, other data (calibration values, standard values, defaultcontrol, etc.) may be entered via the keyboard associated with theanalyzer for interface with the computer program. The floppy disk driveis used to add new information to the hard disk. The electronics of theanalyzer control means typically include printed circuit boards thatcontrol such elements as the motor drivers, ultrasonic transducer,heaters, temperature sensors, and luminometer.

The analyzer of the invention desirably includes a computer monitorhaving a display screen on which the computer program displaysinformation to the operator and information guiding an operator ininputting sample identification information. In addition to providingsample identification information and analyte test requests into thecomputer, the operator can instruct the computer give the processing ofa particular sample high priority.

When a tray of reagent packages or sample cups is placed in theanalyzer, the bar code label information may be read and fed to theelectronics for processing by the computer program. In the analyzershown in FIG. 1, 6 sample trays, each containing 10 samples, can beprocessed at one time. Each sample will be assigned a tray position asit is placed in the analyzer and the information identifying the sampleand the tests to be performed on the sample enter by the operator. Eachnewly entered test request is stored in a computer file referred toherein as a worklist, with all the other test requests in progress orpending. The tests requests are processed by the analyzer control meansas described below.

FIGS. 9 and 10 show flow charts of the scheduling logic of an analyzercontrol means 200 of the preferred analyzer and FIG. 11 depicts anactual scheduling sequence for six samples. Referring first to FIG. 9,this flow chart depicts the scheduling logic for a test having aone-stage assay protocol, i.e., a protocol where the assay constituentsin a reaction vessel are incubated, washed and read sequentially. First,the control means determines whether the assay resource or resourcesnecessary to begin a desired test is available at the start of the nextcycle of the analyzer, which in this embodiment is the start of the nextincubator cycle. In the preferred analyzer described herein, the firstassay resource that must be available is the assay constituents deliverymeans. If the delivery means is scheduled to be performing anotherfunction at that time, such as delivering reagents to a reaction vesselcontaining assay constituents of a two-stage protocol test, the controlmeans will check successive cycles to determine the first availablecycle when the assay constituents delivery means is available.

When an available cycle for the delivery means to operate has beenidentified, the controller determines whether transfer to the wash wheeland the wash station operations will be available at the appropriatetime to act on the reaction vessel if the delivery means began itsoperation during that first available cycle. As described above, in thisembodiment the dwell time of a vessel in the incubator can be expressedas a multiple of the indexing time of the incubator, i.e., an integralnumber of indexing cycles of the system. In FIG. 9, this number isdenoted as "x" and the control means determines whether a position isavailable on the wash wheel that will take a reaction vessel through thewash station at "n+x" indexing cycles, or x indexing cycles after theassay constituents were added to the vessel. If a reaction vessel isalready scheduled to enter the wash wheel at the "n+x" time slot, thecontrol means determines the next available cycle for the deliverymeans, indexing "n" each time, until it determines that an "n+x" timeslot will be available on the wash wheel if the assay constituents areadded to a reaction vessel during the cycle when the delivery means isavailable.

Before processing of the test begins, the control means must alsodetermine on a cycle-by-cycle basis when the reaction vessel can betransported to the read station. In this embodiment, a vessel will reachthe read station an integral number "y" indexing cycles of the incubatorafter the vessel has been transferred onto the wash wheel at the firstwash transfer station. Although "x" may vary between test protocols, "y"will be constant for all protocols because the wash wheel moves in afixed cycle. If the read station is not available at the time slot"n+x+y", the control means will check the availability of all the assayresources on a cycle-by-cycle basis until a time when at initiation ofprocessing at a time slot "n" all the necessary assay resources will beavailable at the appropriate time.

Once the control means determines a suitable initiation time slot "n"for a test, it will schedule the test to begin processing at time "n"and it will allocate the assay resources to that test according to thetime-based requirements of each of the necessary assay resources. Thus,it will schedule the reaction vessel designated for that test to enterthe wash wheel at time slot "n+x" and move to the read station at timeslot "n+x+y". When the control means determines a suitable initiationtime slot "n" for a second test, it must check the availability of thetime-based assay resources requirements of that second test against theallocation of assay resources for any previous test.

FIG. 10 shows a similar flow chart depicting the scheduling logic of thecontrol means for a test having a two-stage protocol. Comparing FIGS. 9and 10, the first two scheduling steps are the same for a one-stage testprotocol and a two-stage test protocol. After a reaction vessel has beenacted upon by the wash station, it must be transferred back to theincubator belt where additional reagents may be added. Accordingly, asthe next step in the scheduling logic, the control means must determineif the assay constituents delivery means, rather than the read station,is available at time "n+x+y." If the assay delivery means is available,the control means must check to see whether a position on the wash wheelwill be available after a second incubation time "z". Finally, if aposition on the wash wheel is available, the control means mustdetermine if the read station will be able to act on the reaction vesselwhen it reaches that station. As discussed above, if a position on thewash wheel is available, generally, the read station will be available.When a suitable initiation time slot has been determined by the controlmeans, it will allocate the necessary resources to that test, preventingscheduling of subsequent tests for the assay resources at those timeslots.

FIG. 11 shows an exemplary schedule for a series of six patient tests.Tests 1, 2 and 6 are each two-stage assays having first and secondincubation times of five indexing cycles. In the preferred embodiment,the indexing time of the incubator is 36 seconds, resulting inincubation times of approximately three minutes. Tests 3, 4, and 5 areall one-stage assays having incubation times of eight indexing cycles,or in the preferred embodiment, incubation times of about 4 minutes and48 seconds.

In this hypothetical schedule, the tests are conducted in order of theirsample numbers. Since no other tests have been previously scheduled,test one of sample one is immediately initiated and the time-based assayresources necessary for its processing are allocated to it on acycle-by-cycle basis, with its processing beginning at indexing cycle"0". The test protocol requires a five indexing cycle incubation, so xequals 5. The reaction vessel containing the assay constituents isscheduled therefore to be transferred from the incubator belt at thefirst wash transfer station and enter the wash wheel at the fifthindexing cycle. In this embodiment, the reaction vessel will betransported through the wash station from the first wash transferstation to the second wash transfer station in approximately 3 minutes.In the preferred embodiment, the incubator indexing cycle is three timesthe wash wheel indexing cycle. Therefore, in 15 wash wheel cycles or 5indexing cycles, the reaction vessel will be positioned adjacent thesecond wash transfer station with a 36-second indexing cycle, this yielda time of about three minutes during which the vessel is moved along thewash-cycle path. The control means has scheduled the assay constituentsdelivery means at time slot 10 to dispense additional reagents into thereaction vessel, denoted in FIG. 11 as 1.2 and positioned on the vesselchain and transfer the vessel back to a position on the incubator belt.The reaction vessel is then transferred back onto the wash wheel atindexing cycle number 15. The reaction vessel will move through the washstation and then to the read station "y" indexing cycles later, or atindexing cycle number 20.

Since the second test has the same assay protocol as the first test, thecontrol means will transport the vessel through the analyzer, allocatingeach of the necessary assay resources to it one indexing cycle after theindexing cycle allocated for the first test. Thus, the assayconstituents for the second test will be delivered to a reaction vesselby the assay constituents delivery means at indexing cycle 1; thereaction vessel will be positioned to transfer to the wash wheel atindexing cycle 6; and the vessel will be transferred to the incubationtransfer station and onto the vessel chain for addition of assayconstituents at indexing cycle 11; the reaction vessel will betransferred to the wash wheel a second time at indexing cycle 16; and itwill be transferred to the read station at indexing cycle 21.

Test three has a one-stage assay protocol. In this example, theincubation time for this test is 8 indexing cycles. Accordingly, thecontrol means will first determine which time-based assay resources arerequired to process the test and it will then check the availability ofthose assay resources on a cycle-by-cycle basis against the allocationof the resources to the processing of tests one and two. Since theincubation time is eight indexing cycles the reaction vessel will beready to transfer to the wash well at indexing cycle 10, eight indexingcycles after the test is initiated if it is initiated at indexing cycle2. Neither of the reaction vessels of test one or test two is scheduledto be transferred to the wash wheel at indexing cycle 10 so processingof test 3 can be initiated at indexing cycle 2 if the read station willbe available at indexing cycle 15; in the preferred embodiment this willalways be the case. Test 4 and 5 in this example have one-stageprotocols as did test 3. Hence, absent any conflicts in the allocationof assay resources, processing of the reaction vessels of tests 4 and 5will sequentially follow the reaction vessel of test 3, by one or twoindexing cycles respectively. As can be seen from FIG. 11, no schedulingconflicts exist for either test 4 or test 5 in this example.

In this example, test 6 has a two-stage assay protocol. The controlmeans will first determine the time-based assay resources necessary forthis test on a cycle-by-cycle basis. The control means will then checkthe allocation of assay resources to the tests in process to determinethe availability of each of the necessary resources for test 6. In thisexample, the control means would identify a conflict if test 6 isinitiated at indexing cycle 5. As shown in FIG. 11, the reaction vesselof test 3 is scheduled to be transferred to the wash wheel at indexingcycle 10, which is the same cycle the reaction vessel for test 6 wouldbe scheduled for transfer to the wash wheel if initiated at indexingcycle 5. Since the control means has already allocated the wash stationresource to test 3 at that time slot, the control means will beginchecking for the availability of resources for test 6 if processing isinitiated at indexing cycle 6. In this example, initiation of theprocessing of test 6 will be delayed until indexing cycle 8, when allthe necessary assay resources will be available for processing test 6 atthe appropriate time.

In the example shown in FIG. 11 the tests were processed in order ofplacement on the analyzer by the operator. In use, the control means ofthe analyzer advantageously optimize the scheduling of a plurality ofanalyte tests for patient samples for which the necessary identifyinginformation has been provided. In the above example, the scheduling ofthe tests could be rearranged so that test 6 would be initiatedimmediately after test 2, and then tests 3, 4, and 5 would be initiatedin each successive indexing cycle. Such scheduling by the control meansreduces the overall number of indexing cycles necessary to complete theprocessing of all the tests thus decreasing total processing time andincreasing throughput. The control means schedules tests to maximizethroughput using an optimization routine.

The method of the invention will be further described with reference tothe timing diagrams of FIGS. 12A and 12B. As shown, a time line extendsto the right of each analyzer element, with a broad band on the timeline indicating a period of time during which the element operates andthe narrower horizontal line indication when the element remains idle.The open boxes along some of the time lines (e.g., the "RAKE") representtime slots when the element may operate if necessary, but will notnecessarily do so. One cycle of the analyzer is shown on 12A and 12Bfrom T₀ to T₀. The fixed cycle may be of any length, although in thisembodiment, one time division equals about 2500 ns.

As described above, a predetermined amount of sample and predeterminedamounts of reagents must be transferred to a reaction vessel to initiatethe processing of an assay. In a preferred embodiment, these assayconstituents are transferred to the reaction vessel by the assayconstituent delivery means, the means including a pipetting probe 42.The lateral and vertical movement of this probe are represented by thetime lines in FIGS. 12A and 12B labelled PIP X-CMPT and PIP Z,respectively. The probe 42 is normally in its lowered position where itmay be positioned within a well of a reagent pack, reaction vessel,sample cup or the like. As shown the probe is raised to its higherposition as it is moved laterally so the probe will not strike the wallsof a reagent pack or a reaction vessel.

Once the operator has entered information identifying a sample and thetest to be performed on the sample, the analyzer control means willposition the inner and outer carousels 22, 30 of the assay constituentssupply wheel (designated as "reagent carousel" and "sample carousel",respectively) are move to position the desired reagent pack and samplecup for access by the probe. Starting at about T₆ the probe beginsaspirating and dispensing volumes of sample and the necessary reagentsto the reaction vessel. After each sample or reagent is dispensed intothe reaction vessel, the probe is lifted up, moved laterally to theprobe washing station 44, and lowered into that station. A cleaningsolution, represented as buffer on FIG. 12, is dispensed through theprobe into the drain cup.

Certain analyte tests are particularly sensitive to cross-contamination.For these tests, a special, more through washing procedure may beinitiated before a second sample is transferred to the reaction vessel.This special wash is shown on FIG. 12 by the operation of the specialwash pump (SPEC WASH PUMP) and corresponding special wash valve (SPECWASH VLV). After the special wash, the pipetting probe is raised andmoved to a reagent well where in this embodiment magnetic particles arestored. The reagent well could contain any reagent.

As described above, the probe may be ultrasonically activated to mixfluids, to level sense and to aid in cleansing of the probe. Theseoperations are reflected in the time lines labeled "LVL SENSE" and"ULTRASONIC-MIXING". As shown in FIG. 12, the pipetting probe tip isultrasonically activated at the end of each wash to aid in cleansing anddrying of the probe. The probe is also activated when it is inserted inthe reagent well containing the magnetic particles prior to aspirationof the particles.

The "PRB WASH VAC VAL" refers to probe wash vacuum valve that refers tothe operation of a valve that turns on and off the vacuum associatedwith the probe washing station 44 in the embodiment described above.

The time lines labeled "DRD PUMP" and "DRD VALVE" represent the times inthe operation of the analyzer when a pump such as the dual resolutionpump used herein operates the aspiration and dispensing operations ofthe pipetting probe.

The "SHUTTLE" time line shows when the vessel chain 70 is operated toposition a reaction vessel into position so that the assay constituentdelivering means can dispense the assay constituents. As explainedpreviously, a reaction vessel receiving assay constituents is desirablypositioned on the vessel chain rather than on the incubator belt 54 tothat the incubator belt may be moved during the pipetting operations ofthe probe. The vessel chain is retracted one position at about T₂ toproperly position a new vessel for delivery. The probe will transfersample and all the reagents required for the chosen analyte test to thereaction vessel during one cycle of the analyzer. The assay constituentcontaining vessel will then be prepared to be transferred to theincubator belt during the next cycle.

In order to transfer the reaction vessel to the incubator belt, thechain is advance two positions ("ADV2") and the incubator belt isindexed forward one position to permit transfer of the vessel to thebelt. This movement of the incubator belt is shown along the time linelabeled "INCUBATION BELT" between about T₁ and about T₂. "SHUTTLE XFER"refers to the incubation transfer station. As described above, if awashed vessel is moved from the wash wheel to the incubator belt at the"WASHOUT XFER" (second wash transfer station) and to the shuttle xfer asthe shuttle (vessel chain) advances two positions the washed vessel willbe positioned for disposal into the waste bag.

The "RAKE" time line refers to the movement of the plurality of fingersin the new vessel loader 72. A new row of vessels will be advanced onlywhen necessary.

An important feature of a method of the invention can be seen bycomparing the time lines and movements of the incubator belt and washwheel. The wash wheel is advanced a fixed distance within each of itsfixed-duration time cycles. As shown on the wash wheel time line, in apreferred embodiment the advancement occurs three times during eachfixed cycle of the analyzer, in this embodiment one indexing cycle ofthe incubator belt. The wash wheel in the embodiment shown is advancedevery five time divisions in FIG. 12, with a first advancement occurringat about T₃.4, the second movement at about T₈.4, and a third movementtaking place at about T₁₃.4. It should be noted that in the embodimentshown, one analyzer cycle equals about 15 time divisions (T_(O) -T_(O)),the time between the third index of the wash wheel and its next indexingat T₃.4 of the next cycle, about five time divisions.

Comparing the incubator belt and wash wheel time lines shows that thetwo assay resources are never scheduled to move at the same time. Whenthe wash wheel is moved the incubator belt remains stationary. The sameis true of the vessel chain ("shuttle" in FIG. 12) and the incubatorbelt-they are never scheduled to move at the same time. At other timesduring the fixed cycle of the analyzer the incubator is free to move.This permits any desired vessel to move along the incubation pathcarried by the incubator belt to a desired transfer location withoutinterfering with the operation of any other assay resource.

Six time lines shown in FIG. 12 reflect the timing of the operation ofcomponents associated with the wash cycle. The vertical movement of thepipette associated with dispensing wash solution and the operation ofthe associated pump and valve are depicted in the time lines labeled"WASH PIP Z", "WASH PUMP", AND "WASH VALVE", respectively. Similarly,the time lines labeled "WASTE PUMP" AND "WASTE VALVE", respectively areboth associated with the aspiration of fluid. The time line labeled"MIXER MOTOR" indicates the operation of the mixing means describedabove in the description of a preferred embodiment. When mixing means ofthe type described herein is used, the motor causes the rotating meansthat removably attaches to the top of reaction vessel to rotate first ina forward, clockwise direction, and then to a counterclockwise rotation,and then once again in a clockwise rotation.

The time lines of a substrate valve and substrate pump, ("SUBST VLV" and"SUBSTR PUMP") elements of the substrate delivery means are shown inFIG. 12.

The "VAC PUMP" time line depicts the continuous operation of a vacuumpump that supplies vacuum to those components of the analyzer requiringvacuum. The operation of the vacuum with respect to those components iscontrolled by the opening and closing of the respective valves.

The operation of the signal detecting means is indicated in FIG. 12along the time line labeled "READ LUMIN". The luminometer is activatedduring the second indexing cycle of the wash wheel, when no reactionvessel is positioned adjacent the luminometer and a series of baselinemeasurements ("dark counts") are made. (As explained in detail the washstation and read stations of a preferred embodiment of the analyzer, arephysically integrated on the wash wheel). The wash wheel then indexesforward placing a sample-containing reaction vessel adjacent theluminometer. The luminometer then takes a series of readings, measuringthe signal generated. The amount of signal generated can be correlatedwith the amount of analyte present in the sample and a final test resultobtained.

While a preferred embodiment of the present invention has beendescribed, it should be understood that various changes, adaptations andmodifications may be made therein without departing from the spirit ofthe invention and the scope of the appended claims.

What is claimed is:
 1. An automated chemical analyzer for automaticallyanalyzing a plurality of samples for at least two different analytescomprising a plurality of assay resource stations each including anassay resource capable of performing a predetermined operation upon asample-containing reaction vessel within a first indexing time, thefirst indexing time defining a time cycle of fixed duration; andanalyzer control means comprising scheduling means for allocating assayresources to one of the reaction vessels as a function of an integralmultiple of said time cycle and transfer control means for controllingtransfer of reaction vessels directly from one assay resource station toanother according to a chronology selected from a plurality of differentpredetermined chronologies, and where at least one chronology requires areaction vessel to be acted on by at least two assay resource stationsmore than once.
 2. The analyzer of claim 1 wherein each assay resourcestation has a predetermined operational sequence during which any of theassay resources of said station is available to perform itspredetermined operation, each of said operational sequences being of aduration that begins and ends during a period of time equal to the firstindexing time.
 3. The analyzer of claim 2 wherein a first and second ofsaid assay resource stations each defines a path of travel for reactionvessels, and comprises transport means for releasably receiving andtransporting sample-containing reaction vessels along the travel paths.4. The analyzer of claim 3 wherein the travel paths of the first andsecond assay resource stations intersect one another at first and secondtransfer stations, each of the transfer stations being adapted toselectively transfer a reaction vessel from one of the first and secondassay resource stations to the other of the first and second assayresource stations.
 5. The analyzer of claim 4 wherein the first assayresource station is maintained at a substantially constant elevatedtemperature.
 6. The analyzer of claim 3 wherein the second assayresource station's transport means has a second indexing cycle having asecond indexing time and transports the reaction vessels along itstravel path a fixed distance during each second indexing cycle.
 7. Theanalyzer of claim 6 wherein the first indexing time is an integralmultiple of the second indexing time.
 8. The analyzer of claim 7 whereinthe first indexing time does not equal the second indexing time.
 9. Anautomated chemical analyzer for automatically analyzing a plurality ofsamples in separate reaction vessels for at least two differentanalytes, comprising a plurality of assay resource stations throughwhich each of said reaction vessels must pass, each assay resourcestation including an assay resource capable of performing apredetermined operation upon one or more of the reaction vessels withina first indexing time, the first indexing time defining a time cycle offixed duration; and analyzer control means comprising scheduling meansfor allocating assay resources to one of the reaction vessels as afunction of an integral multiple of said time cycle and transfer controlmeans for controlling transfer of the reaction vessels directly from oneassay resource station to another according to a chronology selectedfrom a plurality of different predetermined chronologies, and where atleast one chronology requires a reaction vessel to be acted on by atleast two assay resource stations more than once.
 10. The analyzer ofclaim 9 wherein a first and second of said assay resource stations eachdefines a path of travel for the reaction vessels and comprisestransport means for releasably receiving and transporting the reactionvessels long the travel paths.
 11. The analyzer of claim 10 wherein thetravel paths of the first and second assay resource stations intersectone another at first and second transfer stations, each transfer stationbeing adapted to selectively transfer one of the reaction vesselsdirectly from one of the first and second assay resource stations to theother of the first and second assay resource stations.
 12. The analyzerof claim 10 wherein the second assay resource station's transport meanstransports the reaction vessels thereon along its travel path a fixeddistance during each of said time cycles and the first assay resourcestation's transport means transports the reaction vessels thereon alongits travel path a variable distance during each of said time cycles. 13.The analyzer of claim 10 wherein the second assay resource station'stransport means has a second indexing cycle having a second indexingtime and transports the reaction vessels along its travel path a fixeddistance during each second indexing cycle.
 14. The analyzer of claim 13wherein the first indexing time is an integral multiple of the secondindexing time.
 15. The analyzer of claim 14 wherein the first indexingtime does not equal the second indexing time.
 16. The analyzer of claim11 wherein the first transfer station is adapted to transfer one of thereaction vessels from the first assay resource station directly to thesecond assay resource station or from a third assay resource stationdirectly to the first assay resource station.
 17. The analyzer of claim16 wherein the second transfer station is adapted to selectivelytransfer one of the reaction vessels from the second assay resourcestation directly to the first assay resource station or the third assayresource station.
 18. The analyzer of claim 1 comprising a first assayresource station which is a pipetting means, and a second assay resourcestation which is an incubator belt, wherein said first assay resourcestation is adapted to act upon a reaction vessel during a prior indexingtime and act upon said vessel during a subsequent indexing time, andwherein said second assay resource station is adapted to act upon areaction vessel during a prior indexing time and act upon said vesselduring a subsequent indexing time, and wherein said vessel is acted onby another assay resource station between the prior and subsequentindexing times.
 19. The analyzer of claim 9 first assay resource stationwhich is a pipetting means, and a second assay resource station which isan incubator belt, wherein said first assay resource station is adaptedto act upon a reaction vessel during a prior indexing time and act uponsaid vessel during a subsequent indexing time, and wherein said secondassay resource station is adapted to act upon a reaction vessel during aprior indexing time and act upon said vessel during a subsequentindexing time, and wherein said vessel is acted on by another assayresource station between the prior and subsequent indexing times.